This invention relates to bulk containers of the type used to store and transport large quantities of agricultural produce, and industrial and other products.
Bulk containers are used for the storage and transport of large quantities of various kinds of items, such as agricultural produce, industrial products and the like. Such a container is disclosed in U.S. Pat. No. 5,180,064 issued Jan. 19, 1993 for "CONTAINER", the disclosure of which is hereby incorporated by reference. The bulk container disclosed in the '064 patent is a one piece molded plastic container having compound formed front, rear and side portions joined by a base wall portion. The base wall portion is elevated from the bottom of the container by means of integrally formed leg sections extending front to rear which support the container on the ground or some other support surface. The two outer leg sections are provided with removable foot members formed in the shape of channel sections which are removably inserted into the hollow underside of the foot portions. Integrally molded corner column support portions provide structural reinforcement for the container. The '064 container is also provided with a novel integral slide entry both fore and aft to facilitate the entry of the tines of a forklift along the underside of the container from either the front or the rear when the container needs to be elevated or transported to another location. The integral slide entry includes a plurality of longitudinally extending arcuate ribs formed along the underside of the base wall portion and extending outwardly of the containment wall portion of the front and rear portion.
Bulk containers are designed not only for individual, free standing use but also for stacking so that the containers and their contents can be efficiently stored and transported. For this purpose, most bulk containers have a bottom external support structure dimensioned to be partially accommodated within the inner periphery of the top rim of another like container for stacking. More particularly, the bottom edge of the container base (or the foot members in the case of the '064 container) typically extends laterally inwardly and then downwardly so as to be received within the inner periphery of the top rim of the underlying container. When stacked, the outer bottom edge of the upper container engages at least portions of the upper surface of the rim of the lower container, so that the vertical load of the upper container is distributed through the engaged portion of rim and the wall structure of the lower container. This design requires that the rim and wall portions have substantial strength in order to support the load of the upper container. While this does not pose a problem for containers made of structurally rigid materials, such as steel, problems are encountered with containers fabricated from substantially less rigid materials, such as molded plastics. In addition, the vertical load imposes substantial stress on the joint between the lateral extension and the downward excursion of the bottom edge of the upper container due to the cantilevered nature of the mechanical configuration. As a consequence, this part of the container typically experiences premature failure unless reinforced by additional strengthening pieces or the provision of thicker amounts of material where the maximum forces are encountered.
Bulk containers should also ideally be designed to outside dimensions which afford a maximum containment volume while still not exceeding the maximum dimensions required for warehousing or transporting such containers in transport trucks and rail cars. The '064 bulk container sacrifices some available internal containment volume by virtue of the fact that the containment wall portions of the front, rear and side portions are displaced inwardly of the outer surfaces.